Basket for radioactive-waste container

ABSTRACT

A radioactive waste container according to the invention has a waste-holding basket formed of two layers of respective dissimilar materials. The layers have faces engaging each other and are bonded together over their entire engaged faces.

FIELD OF THE INVENTION

[0001] The present invention relates to a radioactive-waste container.More particularly this invention concerns a basket adapted to hold spentfuel rods or the like in a radioactive-waste container.

BACKGROUND OF THE INVENTION

[0002] As described in U.S. Pat. No. 6,256,363 a transport/storagecontainer for spent nuclear-fuel elements has a vessel having a sidewall with an inner surface defining an interior extending along an axisand a plurality of like sections forming a basket extendingsubstantially a full axial length of the interior and forming aplurality of axial full-length rectangular-section wells adapted toreceive the spent fuel elements. Each of the sections is formed of twolong light-metal neutron-absorbing plates crossing each other, eachhaving a pair of outer ends directly engaging the inner surface of theside wall in heat-transmitting contact therewith, and subdividing theinterior at the respective section into a plurality of segments. Aplurality of short light-metal neutron absorbing plates are fittedtogether in each of the segments and form with the main plates of therespective section rectangular-section axially throughgoing openingsforming the wells with the plates of the other sections.

[0003] Such a basket fulfills several functions. First of all itphysically contains and separates the radioactive elements being storedor transport from one another, to which end it must be fairly strong asthese rods are very heavy. Furthermore it must have goodneutron-shielding capacity for obvious shielding purposes. Finally thebasket must be able to conduct heat readily from the decaying elementsto the outer wall of the container.

[0004] As a result the basket is typically made of sheet or platematerial having at least two layers. One layer is selected for strengthand heat transmission and typically is high-strength stainless steel.The other layer is typically a boron-alloyed or boron-containing metalwhose primary function is maintaining subcriticality, or shielding. Inaddition it is possible to use also copper or aluminum to maximize heattransmission.

[0005] These layers are very difficult to join together. Typically weldsare used, which means that there are gaps or spaces between the layers.As a result, heat transmission is reduces because of the spaces.Furthermore these spaces can trap water and create subsequent corrosionproblems. Finally the welding invariably weakens at least theboron-containing layer, reducing the overall strength of the basket. Theonly way to make such a multilayer basket strong enough is to use fairlythick plate material, increasing the weight of the basket and reducingthe space available for the radioactive material being stored.

[0006] Another disadvantage of the known systems is that they are fairlyexpensive to manufacture. The techniques for welding together suchdisparate materials are somewhat complex, and at best yield poorresults.

OBJECTS OF THE INVENTION

[0007] It is therefore an object of the present invention to provide animproved basket for a radioactive-waste container.

[0008] Another object is the provision of such an improved basket for aradioactive-waste container which overcomes the above-givendisadvantages, that is which shields and conducts heat well and that isquite strong.

SUMMARY OF THE INVENTION

[0009] A radioactive waste container according to the invention has awaste-holding basket formed of two layers of respective dissimilarmaterials. The layers have faces engaging each other and are bondedtogether over their entire engaged faces.

[0010] Joining the two layers of the basket over their entire surfacesensures that there are no air gaps between them, greatly increasing thestrength of the assembly even though it might include a relatively weakboron-containing metal. Furthermore the elimination of any air spacesbetween the layers ensures that heat will be efficiently transmitted bythem to the surrounding container. The layer of radiation-blockingmaterial is also continuous and of uniform thickness so it offersmaximum shielding with no leak spots.

[0011] The surface bond with no spacing according to the invention canbe done by roller plating, that is rolling together two sheets of metalunder very high pressure with or without an intermediate bonding layer,by high-pressure hydroforming in particular when nonflat shapes areneeded, or even by explosive plating. What is important in accordancewith the invention is that the confronting surfaces of the two layersare joined together at the molecular level over their entire abuttingsurfaces, with or without the interposition of an intermediate bondinglayer with which both layers are molecularly bonded.

[0012] In accordance with the invention one of the layers is made ofcopper, a copper alloy, aluminum, an aluminum alloy, borated stainlesssteel and/or a boron-containing metal alloy and the other layer is madeof high-strength stainless steel. The high-strength steel layer acts asthe support and supplies most of the strength to the basket while theother layer functions more for shielding. Both layers can conduct heataway and, since they are intimately joined together, will conductbetween each other very efficiently.

BRIEF DESCRIPTION OF THE DRAWING

[0013] The above and other objects, features, and advantages will becomemore readily apparent from the following description, reference beingmade to the accompanying drawing whose sole figure is a largelydiagrammatic representation of the invention.

SPECIFIC DESCRIPTION

[0014] As seen in the drawing a spent radioactive fuel rod shown partlyat 3 is held in a container shown partly at 4 in a similarly partiallyshown basket comprised of a pair of layers 1 and 2. The layers 1 and 2have confronting faces 1′ and 2′ that are secured molecularly togetherat a bond 5 that extends over the entire areas of these faces 1′ and 2′.This bond 5 is produced here by roller plating, that is pressing twosheets or plates together between rollers with such force that they bondtogether.

[0015] In accordance with the invention the layer or lamina 1 is made ofcopper, a copper alloy, aluminum, an aluminum alloy, borated stainlesssteel and/or a boron-containing metal alloy. The other layer or lamina 2is made of high-strength stainless steel. The two layers 1 and 2 areunitarily joined together at the faces 1′ and 2′ in surface contact,that is bonded on a molecular level.

[0016] The bond 5 can also be a sheet bonding layer between the faces 1′and 2′ unitarily bonding same together.

We claim:
 1. In a radioactive waste container, a waste-holding basketformed of two layers of respective dissimilar materials, the layershaving faces engaging each other and being bonded together over theirentire engaged faces.
 2. The basket defined in claim 1 wherein one ofthe layers is made of copper, a copper alloy, aluminum, an aluminumalloy, borated stainless steel or a boron-containing metal alloy and theother layer is made of high-strength stainless steel.
 3. The basketdefined in claim 1 wherein the layers are joined unitarily in surfacecontact.
 4. The basket defined in claim 1, further comprising a layer ofbonding material between the faces unitarily bonding the layerstogether.